FOR THE THIRD YEAR in a row, the Soviet

grain harvest is expected to fall far short--by 40 million to 50 million tons--of the official goal. Russian agricultural areas suffer from hard winters, a short growing season and frequently, as this year, low rainfall. But production suffers even more from the inefficiencies of a system designed with factory workers in mind.

Even with modern machinery, farming is an around-the-clock job. As the disappointing production of Soviet collective farms reveals year after year, it cannot be done well by workers who are waiting for the whistle to blow or who feel no personal tie to the land they farm. Failures in other sectors of the Soviet economy--a lack of tractors, for example--are also crippling. Many of these shortages are the result of resources having been diverted to meet military needs.

Coming on top of two previous bad years and Jimmy Carter's grain embargo, this harvest will be felt throughout the Soviet economy. Not only will grain be short, but because of the lack of animal feed, so will meat and dairy products. Informal rationing has already been instituted. The government will be forced yet again to postpone its long-held goal of improving the domestic diet. The commitment made to supply various foodstuffs to Poland will exacerbate the shortages and worsen citizen discontent.

Worst of all, from the Kremlin's point of view, the shortage will force the government to import very large amounts of grain, using up much of the country's hard currency earnings, which the government would much prefer to spend purchasing Western high technology. The imports also constrain foreign policy options, since most of the world grain trade is supplied by the United States, Canada and Australia and could be cut off in the wake of, for example, an invasion of Poland.

The harvest's economic repercussions will not be limited to the Soviet Union. Heavy Russian buying in international markets will drive up food prices in the United States, benefiting farmers but hurting consumers and slowing efforts to control inflation. In spite of the president's constitutional dislike of anything that smacks of interference with free trade, the administration needs to decide in advance approximately how much grain the United States will sell to the Soviet Union. It is the sudden and unanticipated sales, like those of 1975, that drive commodity prices sky high. sales, like those of 1975, that drive commodity prices sky high.